Tree shearing device

ABSTRACT

A tree shearing apparatus is provided which cuts virtually all of the wood fibers at an oblique angle thereto thus reducing power requirements by improving the shearing action. Upward compression and/or splitting forces on the trunk are very significantly reduced as compared with the prior art devices and provision is made for a major portion of the compressive forces to be transmitted downwardly to the stump. An increased recovery of usable wood may also be realized by virtue of the use of the present invention. The tree shearing apparatus includes a support means adapted to be positioned adjacent the trunk of a standing tree. The apparatus includes first and second cutter blades each having a cutting edge mounted to the support means, with the cutter blades projecting generally forwardly from the support means. Means are provided for mounting the cutter blades for motion of their cutting edges along curved paths from elevated positions where the cutting edges are spaced from one another to lower positions where the cutting edges are closely adjacent to one another thereby to perform a tree-cutting operation. The apparatus also includes actuating means for effecting the above noted movement of the cutter blades.

This invention relates generally to shear apparatus for severingstanding trees from their rooted stumps at a location closely adjacentthe ground. More particularly, the invention relates to shear apparatushaving cutting edges that travel in arcuate paths generally towards oneanother whereby to sever the fibers of the tree while effecting minimaldamage to the tree trunk.

Shearing apparatus of the general nature described above is known in theart as, for example, from U.S. Pat. No. 3,461,929 issued Aug. 16, 1969which apparatus includes a pair of opposed cutting blades each mountedon its own shaft with the shafts being spaced horizontally. The cuttingblades are in the form of cylindrical segments. In the particulararrangement described in this patent, the cutting edges of the bladesenter opposing sides of the tree trunk and move along circular pathstowards each other, firstly generally downwardly, then somewhathorizontally, and then slightly upwardly until the tree has been severedfrom the rooted stump. Since the blades are compelled to move almosthorizontally for a substantial distance, many of the wood fibers aresheared at almost right angles thereto thus increasing the powerrequirements for the shear head and increasing the possibility ofcrushing and damaging the wood fibers adjacent the paths of cut.Furthermore, owing to the thickness of the blades and the upward motionof same during the final cutting stage, there is a tendency forsplitting forces to be transmitted to the tree trunk. In addition, anappreciable amount of useable wood material is left in the stump and isthus wasted.

The above noted U.S. Pat. No. 3,461,929 provides for the mounting of theblades on a pair of spaced apart axes, one turning axis and itsassociated blade being located to one side of the vertical center lineof the apparatus, and the other turning axis and its associated bladebeing located to the opposite side of the vertical center line of theapparatus. In an effort to eliminate some of the disadvantagesassociated with the spaced-apart rotation axes for the blades,arrangements have been devised wherein the two opposed blades aremounted for rotation on a common axis located on the vertical centerline of the shear head. Arrangements such as this are shown in U.S. Pat.Nos. 3,817,303 issued June 18, 1974 and 3,862,652 issued Jan. 28, 1975.This form of mounting arrangement substantially eliminates the upwardmotion of the cutting edges during the final cutting stages and reducesthe danger of splitting of the trunk. However, because the blades, ofnecessity, have a finite thickness, substantial upward thrusts are stillapplied to the trunk during the final severing operation. In addition,the blades must still cut a substantial portion of the fibers at rightangles thereto with resulting high power requirements and some crushingof the wood. Furthermore, a certain degree of usable wood is still leftin the stump.

It is a principal object of the present invention to alleviate thedisadvantages above and to provide tree shearing apparatus which cutsvirtually all of the wood fibers at an oblique angle thereto thusreducing power requirements by improving the shearing action. Upwardcompression and/or splitting forces on the trunk are very significantlyreduced as compared with the prior art devices and provision is made fora major portion of the compressive forces to be transmitted downwardlyto the stump. An increased recovery of usable wood may also be realizedby virtue of the use of the present invention.

Accordingly, therefore, the present invention relates to tree shearingapparatus including a support means adapted to be positioned adjacentthe trunk of a standing tree. The apparatus includes first and secondcutter blades each having a cutting edge mounted to the support means,with the cutter blades projecting generally forwardly from the supportmeans. Means are provided for mounting the cutter blades for motion oftheir cutting edges along curved paths from elevated positions where thecutting edges are spaced from one another to lower positions where thecutting edges are closely adjacent to one another thereby to perform atree-cutting operation. The apparatus also includes actuating means foreffecting the above noted movement of the cutter blades.

The invention is particularly characterized, in one aspect, in that themeans for mounting the cutter blades are arranged so that said motion ofeach cutting edge continually has a downwardly directed component ofmotion from said elevated position to said lower position.

In a further aspect of the invention, the means mounting the cutterblades are arranged such that the curved paths each lie in a circulararc, said circular arcs intersecting one another in the region of thelower positions of the cutter blades.

In accordance with a further feature of the invention, the cutter blademounting means includes means defining a pivot axis for each blade. Thepivot axes are spaced apart and the cutter blades are arranged relativethereto such that radial lines drawn from the pivot axes to theirrespectively associated cutting edges intersect one another.

In the preferred form of the invention, the pivot axis defining meansare spaced apart in the horizontal direction and the mounting means forthe cutter blades are arranged such that the curved path taken by eachcutting edge lies to a side of an imaginary vertical plane locatedmid-way between the spaced-apart pivot axes, which side is opposite tothe side of such plane where the pivot axis for such blade is located.

In a further feature of the invention, each blade is arcuately curvedand related to the mounting means in such a fashion as to reducecompression and friction forces between the blade surfaces and the cutsurface of the tree trunk during the tree-cutting operation. In apreferred form of the invention, the inner surface of each curved blade,i.e., the surface adjacent the tree trunk during the tree-cuttingoperation, may be arranged such that it moves slightly away from the cutportion of the tree trunk during the cutting operation.

In a further feature of the invention, it is also desirable that theabove noted inside surface of the blade be smoothly curved from theleading or cutting edge to the trailing edge thereof. Thus, the bevel onthe cutting blade which serves to provide the sharp cutting edge shouldbe located on the outside of the leading edge of the blade, i.e., thesurfaces directed towards the stump thereby assisting in transferringthe bulk of the fiber compressing forces to the stump.

The principles of the invention will be more clearly understood from thefollowing description, by way of example, of preferred embodiments ofthe invention wherein reference is made to the drawings wherein:

FIGS. 1 and 2 diagrammatically illustrate the cutting paths taken byshear blades of tree shearing devices according to the prior art;

FIGS. 3 and 4 diagrammatically illustrate the cutting paths taken byshear blades of tree shearing devices to the present invention;

FIG. 5 is a front elevation view of tree shearing apparatus according tothe present invention;

FIG. 6 is a side elevation view of the apparatus shown in FIG. 5;

FIG. 7 is a section view taken along line 7--7 in FIG. 5;

FIG. 8 is a top plan view of the grapple arm arrangement used in theapparatus of the present invention (all structure below the grapple armassemblies are not shown).

With reference now to the drawings, FIG. 1 diagrammatically illustratesthe movement of the shear blades in accordance with the arrangementdescribed in U.S. Pat. No. 3,461,929. It will be seen that the pivotaxis for blade A is spaced horizontally from the pivot axis for blade B.It will be seen that the cutting path of blade A is a circular arcextending from point a to point a' while the cutting path for blade Bextends from point b to b'. However, because of the particulararrangement of the blade pivot points or axes in relation to theirassociated blades, each blade moves firstly generally downwardly, thensomewhat horizontally, and then finally upwardly for a short distancealong the last portion of the cutting path. Since both blades movealmost horizontally for a substantial distance, many of the wood fibersare sheared at almost right angles thereto thus increasing powerrequirements as well as the possibility of crushing of the wood fibers.In addition the upward motion of the cutting edges during the finalcutting stages tend to transmit splitting forces to the tree trunk.Furthermore, the particular cutting paths utilized leave an appreciableamount of usable wood material in the stump.

In the arrangement shown in FIG. 2, which is representative of the blademotions of the devices shown in U.S. Pat. Nos. 3,817,303 and 3,862,652,it will be seen that blades A B are pivoted about a common axis at thecenter line of the machine. By virtue of this arrangement, the upwardmotion of the cutting edges during the final cutting stages issubstantially eliminated thus reducing the danger of splitting. However,a substantial proportion of the wood fibers in the tree trunk are cut atright angles thereto with resulting relatively high power requirementsfor the device and some crushing of the wood. Furthermore, because theblades must have a definite thickness in order to provide adequatestrength, substantial upward thrusts are still applied to the tree trunkduring the final severing stages. In addition, a certain degree ofrecoverable wood is still left in the stump.

FIG. 3 illustrates the motion of the cutter blades as provided for inaccordance with the present invention. It will be seen that blade A ispivoted at pivot point A and moves from an upward position a to a lowerposition a' while blade B pivoted at point b moves from an upwardposition b to a lower position b' immediately adjacent point a'. Thepivot points A and B are spaced horizontally as in the arrangementdiagrammatically illustrated in FIG. 1. However, the path of motion ofeach blade lies wholly to one side of the vertical center line LCopposite to the side on which its associated pivot point is located. Inother words, as seen in FIG. 3, pivot A is located on the left side ofthe vertical center line while the path of travel of its associatedblade a-a' is entirely on the opposite side of the vertical center line.Pivot point B is located on the opposite side of the center line frompivot point A while the path of travel of blade B, i.e., b-b' is locatedentirely on the opposite side of the vertical center line from pivot B.By virtue of this particular arrangement, the cutting edge of each bladehas a downwardly directed component of motion at all times as the bladesmove from points a and b to points a' and b' respective. The downwardlydirected motion component during the final cutting stages is designatedby reference X in FIG. 3.

By virtue of the fact that the cutting edges always have a downwardlydirected component of motion as the blades move towards one another fromtheir elevated positions to their lowermost positions, the wood fibersin the tree trunk are always being severed at an oblique angle theretothus reducing crushing and reducing power requirements. Furthermore,since the blades always have said downwardly directed component ofmotion, the degree of magnitude of the horizontally directed componentsis correspondingly reduced and it can readily be determined that agreater degree of recovery of usable wood may be achieved, e.g., it ispossible for the cutter blades to, in effect, bite deeper into the stumpthus removing more usable wood therefrom.

FIG. 4 illustrates the effect of the thickness of the blade on thecutting operation. Since the blades must have a predetermined thicknessin order to provide adequate strength, there will, of necessity, be acertain degree of displacement and pushing aside of the fibers of thetree during the cutting operation. However, it is desirable that thisdisplacement take place primarily in the rooted stump. Several differentfactors must be taken into consideration. Firstly, in order to avoidundue compressive and frictional forces between the inside surface ofthe blades, i.e., those surfaces facing the tree trunk, such surfacesmust not lie inside a radial line drawn from the pivot points of therespective blades. In fact, it is preferable that the inside surface ofthe blade be arranged such that it diverges slightly outwardly and awayfrom the circular arc defined by the cutting path of the blade such thatthe inside surface of the blade moves away from the cut portion of thetree trunk and provides a small clearance therebetween as illustrated inFIG. 4. This clearance is illustrated in FIG. 4 by reference C. Inaddition, since the leading edges of the blades must be bevelled inorder to provide the sharp cutting edge, the bevel should be located onthe outside of each blade, i.e., on the side which is most closelyadjacent the stump during the cutting operation. By virtue of thisarrangement, the fibers which are pushed or plowed aside as the bladesmove through the tree tend to be primarily in the stump.

With reference now to FIGS. 5-8 which illustrate a preferred embodimentof the invention, it will be seen that the tree shearing head designatedgenerally by reference numeral 10 includes a generally upright supportpost 12, such post being of rectangular cross-section and being hollowthereby to reduce weight. A tree shear assembly 14 is mounted adjacentthe lower end of support 12, with a tree grapple arm assembly 16 beingmounted to the support 12 above the shearing assembly 14.

The entire shear assembly 10 is adapted to be attached to the bodystructure or articulated or telescopic boom of a tractor or otheruniversal machine (not shown) in the manner well known in the artthereby to enable the operator to place the tree shearing assemblyclosely adjacent the trunk of a growing tree and to effect shearingthereof in the manner generally well known in the art. Accordingly, nofurther description of such conventional equipment for carrying andmanipulating the shearing apparatus is deemed necessary.

In order to grasp the tree to be felled and to center it properlyrelative to the shearing assembly 14, the grapple arm assembly 16includes a pair of opposed grapple arms 18 of the type generally wellknown in the art. The grapple arms 18 have curved tree engaging surfaces20 adapted to closely embrace and securely hold the tree when the arms18 are in "closed" positions. The grapple arms 18 are securely pivotallyconnected to the support post 12 by means of connector brackets 22firmly mounted on support post 12 with associated pivot pins 24 passingthrough such support brackets and their associated grapple arms 18. Thepivot pins 24 define pivot axes for said grapple arms 18 which aregenerally parallel to the longitudinal axis of support post 12. In orderto actuate grapple arms 18, each arm 18 has a hydraulic cylinder 26associated therewith, each hydraulic cylinder 26 being connected at itsone end via bracket 28 and pivot pin 30 to support post 12 with the ramat the opposite end of hydraulic cylinder 26 being pivotally connectedto the associated grapple arm 18 via pivot pin 32 as clearly seen in thebroken away view of FIG. 8.

In order to further center the tree relative to the shear arrangement14, the apparatus further includes a support and centering means 36disposed a short distance above the grapple arm assembly 16. Thissupport and centering means 36 includes a forwardly projecting portion38 having a generally V-shaped intermediate portion 40 into which aportion of the tree trunk may enter thereby to effect the supporting andcentering action referred to above.

The shear apparatus 14 includes an opposed pair of elongated cutterblades 42 and 44, each of the cutter blades 42, 44 having an associatedgenerally sharp cutting edge 42a, 44a associated therewith. Cutter blade42 has a blade mounting assembly 46 associated therewith and arrangedsuch that blade 42 rotates about the pivot axis defined by shaft 48while blade 44 has a blade mounting assembly 50 associated therewith andarranged so that blade 44 rotates about the pivot axis as defined byshaft 52. The blade mounting assemblies 46 and 50 are each substantiallyidentical in construction except, of course, for the fact that they areof opposite hand to one another. Thus, only one of them need bedescribed in any detail. Blade mounting assembly 50 includes a frontplate 54, an intermediate plate 56 and a rear plate 58. Extendingbetween the rear plate 58 and the center plate 56 is a brace plate 60the opposite ends of which are firmly welded to the plates 56 and 58.The center and back plates 56 and 58 are further firmly secured togetherby a further brace plate 62 generally at right angles to the abovementioned brace plate 60. This further brace plate 62 serves to mount abracket 64 having a pair of spaced upstanding lugs 66 thereon whichreceive a transverse shaft member 68 to which is connected the ram of ahydraulic cylinder 70. The blade mounting assembly 50 further includes atop brace plate 72 extending between the front plate 54 and the centerplate 56. In addition, blade 44 is mounted intermediate the front andcenter plates 54 and 56 as best seen in FIGS. 5 and 6 and since bothplate 72 and blade 44 are securely welded at their opposed ends to saidplates, a strong and rigid structure is provided.

The lower end of support post 12 is provided with a spaced apart pair ofgusset plates 74 and 76 securely welded to the front and rear faces ofthe post, such gusset plates having at the lower ends thereof two spacedapart apertures (not shown) thereby to permit passage therethrough ofthe above mentioned pivot axles 48 and 52. Extending through theseapertures and securely welded to gusset plates 74 and 76 are a pair oftubes 78 and 80 as best seen in FIG. 7. The previously mentioned spacedapart parallel pivot shafts 52 and 48 extend through tubes 78 and 80 andare rotatable relative thereto. With reference to blade mountingassembly 50, the center and rear plates 56 and 58 are suitably keyed topivot shaft 52 for rotation therewith and, in order to provide forsynchronous movement of blades 42 and 44, each of the pivot shafts 52and 48 have meshing synchronizer gear assemblies 82 and 84 connectedthereto as illustrated in FIGS. 5, 6 and 7.

Since the center and rear plates 56 and 58 of blade mounting assembly 50overlap the center and rear plates for blade mounting assembly 46, andsince the pivot axle for 48 for blade mounting assembly 46 extendsthrough center and rear plates 56 and 58, each of the latter plates havean arcuate opening 90 therein, the shape of which is best seen in FIG. 5thereby permitting blade mounting assembly 50 to rotate about the axisdefined by shaft 52 without interfering with shaft 48 and its associatedassemblies.

The general characteristics of cutter blades 42 and 44 have beendescribed previously. However, in connection with the particularembodiment shown, it is noted that they are of elongated form and havegenerally straight cutting edges 42a and 44a. The two blades arearcuately curved in cross-section and in the particular arrangementshown, each blade has its inner and outer surfaces arranged to lie inimaginary cylindrical surfaces centered at the pivot axes with whichthey are respectively associated, i.e., the inner and outer surfaces ofblade 42 lie in cylindrical surfaces centered at the pivot axis definedby shaft 48 while the inner and outer surfaces of blade 44 lie incylindrical surfaces centered at the pivot axis defined by shaft 52.However, as noted previously, it may be advantageous in many cases tomodify this shape slightly so that the inner surfaces of the blades moveslightly away from the cut portion of the tree butt during the cuttingoperation. In addition, in order to define the sharp cutting edges 42aand 44a, the blades 42 and 44 include respective bevelled portions 42band 44b, such bevelled portions lying on the outside of the blade, i.e.,that side opposite to the side on which its associated pivot axis islocated thereby to reduce the degree of displacement or crushing of thewood fiber on the tree trunk and to transfer as much of the damage tothe rooted tree stump.

In order to actuate the cutter blade mounting assemblies 46 and 50, apair of hydraulic cylinders 70 are provided on opposing sides of thesupport post 12. The upper ends of the hydraulic cylinders are pivotallyconnected to support post 12 via suitable bracket means 92 andassociated pivot pins 94 while at the opposing ends thereof, the rams ofthe hydraulic cylinders are pivotally connected to the blade mountingassemblies 46 and 50 by the bracket means 66 and pivot pin means 68described previously. When the hydraulic cylinders 78 are actuated bysupplying hydraulic fluid thereto through suitable valve means (notshown), the blade mounting assemblies 46 and 50 are rotated about theirrespective pivot axes thus bringing the cutting edges 42a and 44atogether along the downwardly and inwardly inclined paths shown by thedashed lines in FIG. 5. As noted above, the synchronizer gears 82, 84ensure that the two blades move together in unison thus ensuring thatthe shearing apparatus as a whole remains centered relative to the treetrunk during the shearing operation. The stroke of the hydrauliccylinders 70 is, of course, selected in conjunction with the dimensionsof the associated components to ensure that the cutting edges 42a and44a just barely come together by the time the cylinders 70 reach the endof their travel.

The operation of the tree shearing device according to the inventionwill be readily apparent to those skilled in the art. The severingapparatus 10, attached to the end of an articulated or telescopic boom(not shown) is made to approach the butt portion of the trunk of a treeto be felled, with the blades 42 and 44 positioned in their upwardlylocated spaced apart positions. When the tree trunk is closely adjacentthe apparatus, the grapple arms 18 are actuated so that the trunk ispositioned between the cutting blades 42 and 44 with the grapple arms 18being thereafter closed to firmly grip the tree and center it relativeto the device. Thereafter, the hydraulic cylinders 70 are actuated so asto cause the cutting edges 42a and 44a of blades 42 and 44 respectivelyto travel along the dashed line paths as illustrated in FIG. 5. Afterthe tree has been severed from the stump, the entire apparatus ismanipulated so as to move the tree into a desired position, e.g., ontothe skidding bank of a log transporting machine or onto a feed stationof a tree delimbing device at which location the butt end of the tree isreleased from the felling device by retracting the grapple arms 18 andretracting cylinders 70 so as to move the cutting blades 42 and 44 totheir spaced apart positions as shown in FIG. 5.

I claim:
 1. Tree shearing apparatus comprising: a support means adaptedto be positioned adjacent the trunk of a standing tree, first and secondcutter blades each having a cutting edge, said cutter blades projectinggenerally forwardly from the support means, means mounting said cutterblades to said support means for motion of their cutting edges alongcurved paths from elevated positions where said cutting edges are spacedfrom one another to lower positions where said edges are in closejuxtaposition to one another, and actuating means for effecting saidmovement of said cutter blades between said elevated positions and saidlower positions whereby to perform a tree-trunk shearing operation,characterized in that said means mounting said cutter blades includes apair of shaft means defining a pivot axis for each said blade, saidshaft means being laterally spaced apart and each said cutter bladebeing mounted to a respective one of the shaft means such that radiallines drawn from said pivot axes to their respectively associatedcutting edges intersect one another as said cutting edges are movedbetween their elevated positions and their lower positions.
 2. Treeshearing apparatus according to claim 1 wherein each said blade isarcuately curved and positioned relative to the mounting means in such afashion that one of the surfaces of each blade moves slightly away fromthe cut surface of the tree trunk to reduce compression and frictionforces between the blade surfaces and the cut surface of the tree trunkduring the tree-shearing operation.
 3. Tree shearing apparatus accordingto claim 1 wherein said cutting edge is formed by a bevel on a leadingedge of each blade, said bevel being formed on that surface of the bladewhich faces toward the rooted stump of the tree during the shearingoperation.
 4. Tree shearing apparatus according to claim 1 furtherincluding means for synchronizing the motion of said cutter blades. 5.Tree shearing apparatus according to claim 1 further including grapplearms for engaging and securing the apparatus relative to the tree duringthe shearing operation.
 6. Tree shearing apparatus comprising: a supportmeans adapted to be positioned adjacent the trunk of a standing tree,first and second cutter blades each having a cutting edge, said cutterblades projecting generally forwardly from the support means, meansmounting said cutter blades to said support means for motion of theircutting edges along curved paths from elevated positions where saidcutting edges are spaced from one another to lower positions where saidedges are in close juxtaposition to one another, and actuating means foreffecting said movement of said cutter blades between said elevatedpositions and said lower positions whereby to perform a tree-trunkshearing operation, characterized in that said means mounting saidcutter blades include shaft means defining a pivot axis for each cutterblade, the shaft means being spaced apart in the horizontal directionand each of said cutter blades being mounted to a respective one of saidshaft means such that the curved path taken by each cutting edge lies toa respective one of the sides of an imaginary vertical plane locatedmid-way between the spaced apart pivot axes, which side is opposite tothe side of such plane where the pivot axis associated with such cuttingedge is located.
 7. Tree shearing apparatus according to claim 6 whereineach said blade is arcuately curved and positioned relative to themounting means in such a fashion that one of the surfaces of each blademoves slightly away from the cut surface of the tree trunk to reducecompression and friction forces between the blade surfaces and the cutsurface of the tree trunk during the tree-shearing operation.
 8. Treeshearing apparatus according to claim 6 wherein said cutting edge isformed by a bevel on a leading edge of each blade, said bevel beingformed on that surface of the blade which faces toward the rooted stumpof the tree during the shearing operation.
 9. Tree shearing apparatusaccording to claim 6 further including means for synchronizing themotion of said cutter blades.
 10. Tree shearing apparatus according toclaim 6 further including grapple arms for engaging and securing theapparatus relative to the tree during the shearing operation.